accessing a PCIe register from userspace through kmem or other ways ?

[Luigi Rizzo]

On Thu, Mar 31, 2016 at 11:55 PM, Ryan Stone <rysto32 at gmail.com> wrote:

> On Thu, Mar 31, 2016 at 4:39 PM, John Baldwin <jhb at freebsd.org> wrote:
>
>> On Wednesday, March 30, 2016 11:20:51 AM Jim Harris wrote:
>> > On Wed, Mar 30, 2016 at 10:47 AM, Luigi Rizzo <rizzo at iet.unipi.it>
>> wrote:
>> >
>> > > Hi,
>> > > I'd like to test the rate at which I can access device registers
>> > > on a PCIe card, and was wondering whether I need to patch a device
>> > > driver, or perhaps I can use /dev/kmem once I figure out where
>> > > the registers are mapped ?
>> > >
>> >
>> > You do not need to patch a device driver.  Have you looked at
>> > libpciaccess?  This should give you everything you need.
>>
>> You can also look at what pciconf uses.  (It has a read_config() method
>> that uses an ioctl on an fd of /dev/pci).
>>
>
> pciconf can only access the configuration space, right?  I believe that
> Luigi is more interested in measuring the latency to a register mapped from
> a BAR.
>

​Thank you all for you answers, I will look at libpciaccess.

Yes my goal is to look at the rate and latency for accessing
BAR-mapped registers

cheers
luigi​




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